1. Field of the Invention
The invention relates to an image forming apparatus, a cartridge and a developing apparatus for application to an electrophotographic apparatus such as a laser beam printer or a copying machine and an electrostatic recording apparatus or the like.
2. Description of the Related Art
FIG. 9 of the accompanying drawings shows an image forming apparatus as an example using a conventional developing apparatus. In FIG. 9, the reference numeral 101 designates the main body of the image forming apparatus, which is a printer engine. The reference numeral 111 denotes a cylindrical photosensitive drum, which is an image bearing member, and it is rotated in one direction about the axis thereof. A charging roller 103 is constituted by a mandrel 103a and a rubber material 103b disposed on the mandrel 103a, and uniformly charges the surface of the photosensitive drum 111.
After the surface of the photosensitive drum 111 has been uniformly charged, a laser beam 55 corresponding to the time-series electrical digital image signal of image information is outputted by an exposing apparatus 102, and is turned back toward the surface of the photosensitive drum by a mirror 56, whereby a latent image is formed on the drum 111.
A developing apparatus 208, as shown in FIG. 11 of the accompanying drawings, is provided with runners 209 on the opposite end portions of a developing sleeve 105, which is a developer carrying member, and the runners 209 contact the photosensitive drum 111 to thereby keep a predetermined gap between the developing sleeve 105 and the photosensitive drum 111. The developing sleeve 105 receives a drive force transmitted from a photosensitive drum gear 211 to a developing sleeve gear 212 to thereby effect rotation, and a toner 109 applied onto the developing sleeve 105 flies onto the photosensitive drum 111 in a developing area as soon as a bias is applied to the developing sleeve 105 through a sliding contact (not shown) and effects reversal developing to thereby visualize the latent image formed on the photosensitive drum 111.
The design of the apparatus is such that a developing bias comprising a DC bias and an AC bias superimposed one upon the other is provided between the photosensitive drum 111 and the developing sleeve 105 by an engine controlling portion (not shown) provided with a power source for driving the image forming apparatus, and a high voltage circuit for supplying a bias for forming an image.
The image on the photosensitive drum 111 visualized by the toner 109 is transferred to a transfer material 114 by a transferring apparatus 110. The transfer material 114 is contained in a sheet supplying cassette 117 and is fed by a sheet feeding roller 116, and is synchronized with the image on the photosensitive drum 111 by registration rollers (not shown) and is fed to the transferring apparatus 110. The visible image by the toner 109 transferred to the transfer material 114 by the transferring apparatus 110 is conveyed to a fixing apparatus 115 with the transfer material 114, and is fixed on the transfer material 114 by heat or pressure and becomes a recorded image.
On the other hand, the residual toner 109 untransferred on the photosensitive drum 111 after the transfer is removed by a cleaning blade 113 in a cleaning apparatus 112. The surface of the photosensitive drum 111 from which the toner 109 has been removed is again charged by the charging roller 103 and repeats the above-described process.
As the conventional developing apparatus, a developing apparatus 208 using a magnetic one-component toner, which is a developer, is shown in detail in FIG. 10 of the accompanying drawings. In FIG. 10, the developing sleeve 105 as a developer carrying member is a non-magnetic developing sleeve formed by a pipe of aluminum or stainless steel, and a magnet roll 106 alternately formed with a plurality of magnetic poles N and S is disposed therein immovably relative to the developing sleeve 105.
The surface of the developing sleeve 105 is worked to an appropriate surface roughness so as to be capable of carrying a desired amount of toner. At a location on the developing sleeve 105, as a developer layer thickness regulating member (hereinafter referred to as the developing blade), a developing blade 107a of e.g. urethane rubber or silicone rubber fixed to a supporting metal plate 107b is made to abut against the sleeve with predetermined pressure.
The toner 109 attracted to the developing sleeve by a magnetic force is regulated to a suitable amount by frictional charging by being carried on the developing sleeve, and by the developing blade 107a portion, and thereafter is given appropriate charges (triboelectricities) by frictional charging by being rubbed between the developing sleeve and the developing blade, and is carried to a developing area. The toner 109 carried to the developing area as described above, when a bias is applied to the developing sleeve 105, flies from the developing sleeve 105 and develops the latent image on the photosensitive drum.
In such a developing apparatus as described above, generally with respect to quality confirmation, such as appearance inspection in the assembling step, and the prevention of toner leakage during distribution, it is often the case that as shown in FIG. 12 of the accompanying drawings, the toner is contained in a toner container 104 by a toner seal 50 and the toner does not adhere onto the developing sleeve until the developing apparatus is delivered to the hand of a user. The user, when the user uses a new developing apparatus for the first time, can pull the toner seal 50, for example, toward this side in FIG. 12, to thereby bring about the state of the developing apparatus as shown in FIG. 10, and can bring the developing apparatus 208 into a usable state in which as indicated by the arrow C in FIG. 10, the toner 109 flows from within the toner container 104 toward the developing sleeve 105, and is attracted to the developing sleeve 105.
However, if the user rotates the developing sleeve by mistake with the toner seal 50 remaining provided, when the developing blade is formed of an elastic material such as urethane rubber, there are the problems that the developing blade is turned up in the direction of rotation of the developing sleeve due to the frictional resistance between the developing blade and the developing sleeve, and it becomes impossible to effect uniform and good toner coating, and the problems that deep frictional contact flaws are formed on the surfaces of the developing blade and the developing sleeve, and if thereafter the developing sleeve is coated with the toner to thereby form an image, vertical streaks attributable to the frictional contact flaws will occur on a halftone image or a solid black image (a full-page black image).
Also, for the convenience of the step of assembling or inspecting the developing apparatus in a factory, it is necessary to rotate the developing sleeve in a state in which the toner is absent on the developing sleeve, and there has been required a technique which does not cause frictional contact flaws on the developing blade and the developing sleeve or the turning-up of the developing blade even when the toner is absent on the developing sleeve.
Regarding this problem, it is conceivable to use a lubricant in the frictional contact portion between the developing blade and the developing sleeve. So, it is conceivable to use a slight amount of toner as the lubricant, but depending on the custody situation in a state in which temperature/humidity is very high such as the export by a ship or the transportation in summertime, the toner may sometimes deteriorate and be fusion-bonded on the developing blade and the developing sleeve and therefore, it is not preferable to use the toner as the lubricant.
So, in order to solve this problem, there is a method of using silicone resin particles or the like as the lubricant, and apply them to that surface of the developing blade which abuts against the developing sleeve. As a method of applying the lubricant, there is a method of applying to the developing blade a solution having powder particles dispersed in volatile liquid (the powder particles should have solvent resistance to the volatile liquid), and in this method, powder particles left after the liquid has been completely volatilized are used as the lubricant (this method will hereinafter be referred to as the liquid applying method). It is for uniformly applying the lubricant that the lubricant is once dispersed in the liquid.
Also, Japanese Patent Application Laid-open No. H8-211728 proposes a method of powder-applying a lubricant directly to the developing sleeve. According to this method, improvement can be made over a halftone vertical streak which may occur in a method of applying liquid to the developing blade.
Also, as lubricating particles, use is made of organic materials such as silicone resin, poly-ethylene tetrafluoride, poly-ethylene trifluoride and polyvinylidene fluoride, or an inorganic material such as molybdenum sulfide. Among these, silicone resin is particularly suitable with respect to heat resistance and humidity resistance.
On the other hand, as a technique which does not cause maintenance work, such as the user filling the developing apparatus with the toner when the toner in the developing apparatus has been exhausted, a technique of making the photosensitive drum, the cleaning apparatus, the charging apparatus, the developing apparatus, etc. integral with each other to thereby provide a process cartridge is popular. As shown in FIG. 13 of the accompanying drawings, the photosensitive drum 111, the charging roller 103, the cleaning apparatus 112 and the developing apparatus 208 are united together by packaging 12 and made into an integral type cartridge 206. The process cartridge has the easy maintenance property that when the toner in the developing apparatus has been used up, the process cartridge is simply exchanged relative to a printer main body, whereby a desired image can be easily obtained again, and is designed such that as soon as the toner in the developing apparatus is used up, the other devices end their lives substantially at the same time, and is a technique which enables a stable quality of image to be obtained until the toner is used up.
However, in a case where use is made of the above-described lubricant according to the conventional art, when the lubricant applied to the developing apparatus adheres to the photosensitive member or the charging roller which is charging means due to vibration or the like in the assembling step or by the transportation of the process cartridge, a black spot of the pitch of the charging roller has sometimes occurred on an image in a portion to which the lubricant has adhered because the lubricant is insulative.
Also, if the lubricant is insulative, a faulty image has sometimes occurred due to the charge-up of the developer at the beginning of the use of the developing apparatus.